Apparatus for transporting a dry toner powder cloud in a xerographic printer which uses a tube having walls composed of a grid of phased voltage elements to transport the charged powder particles.
Some xerographic printers use dry toner particles which can be transported from a sump to a target location, such as a charged photoreceptor, by the use of a stationary insulative substrate having a series of imbedded conductive elements in its surface to form a grid. A voltage is applied to the- toner, and phased voltages are applied to the conductive elements, resulting in a toner cloud being transported along the stationary grid. Such a device is described in U.S. Pat. No. 5,717,986 and U.S. patent application Ser. No. 09/613,018, which are incorporated by reference herein.
Most of the toner is reliably carried in this way, but the cloud is subject to local air turbulence, and to a weakened or variable voltage at the edge of the grid, resulting in toner loss or non-uniform transport speed. The edge effect can be minimized by increasing the width of the grid, but at the cost of increasing size and space requirements. A more compact and reliable form would be useful.
An improvement would be to build a laminated structure of alternating layers of insulation and conductors to form a phased array of conductive elements. A hole could then be bored through the laminations to form a tube, through which the toner could be transported. The tube could be of any length and diameter. This arrangement would have several advantages:
Manufacturing costs would be reduced. The diameter of the tube could be reduced to a fraction of an inch without any loss of toner and with no edge problems. Also, the resultant tube could be bent after manufacture to conform to any space/angle requirements that may exist in the printer.
In the alternative, the holes could be formed in the conducting and insulating layers before they are laminated. In this case the internal space could be any shape such as an elongated slot, so that the toner would be ejected at the end of the tube in the form of a sheet instead of a cylinder.